Process for making thioethers



3,440,287 1C6 Patented P 22, 1969 be obtained even when one variable is unfavorable, pro- 3,440,287 vided that the others are optimized. Thus, the Li salt is PROCESS FOR MAKING THIOETHERS a more selective catalyst than the Na salt; the selectivities Lee H. Horsley, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich. a corporation of of the common lower alkylene oxides vary widely in the inverse order of molecular weight, i.e. C C C the D l 3 ig-fix Filed No 24, 1965 Sen 509,607 reaction 15 more selective at low temperatures than at 1 m CL 307 149/10 higher ones and at high oxide/mercaptan ratios than at US. Cl. 260-609 Claims lower ones. By selectivity is meant the favoring of the desired reaction and minimizing of the undesired ones. 10 The catalyst can be added to the reactants as such or ABSTRACT OF THE DISCLQSURE it can conveniently be made in situ by adding the alkali metal or its oxide, alkoxide or hydroxide, or the like, to the mercaptan or to the reaction mixture.

The amount of catalyst is not critical and can be varied widely. In general, large amounts, such as 0.1 mole per mole of mercaptan, cause rapid reaction but show somewhat less selectivity than do smaller amounts. Suitable ratios are about 0.01 to 0.1 mole per mole of mercaptan, the preferred ratio being about 0.02 to 0.06 mole per mole.

The practice of the invention is illustrated by the following examples.

In a series of experiments, the reactants were sealed in a glass ampoule, heated at 100-105 C. during the reaction period, cooled, removed from the ampoules and analyzed by vapor phase chromatography. In each experiment 0.01 mole of mercaptan and the indicated Mercaptans are oxyalkylated to produce Z-hydroxyalkyl thioethers substantially free of polyglycol thioethers by reacting the mercaptan with at least a 3-fold excess of alkylene oxide in the presence of a lithium or sodium mercaptide at a temperature of 80-125 C.

This invention relates to the production of B-hydroxyalkyl thioethers by the reaction of a vicinal alkylene oxide with a mercaptan. In this reaction as practiced heretofore, additional alkylene oxide reacted with the desired product, thus producing a polyoxyalkylene (i.e. polyglycol) thioether. Heretofore, attempts have been made to minimize this side-reaction by using less than the stoichiometric amount of alkylene oxide (i.e. by the use of excess mercaptan). In many cases this poses a separation problem because the mercaptan and the desired thioamount z and alkylfine Oxide Were reacted ether often boil near the same temperature. n er a nitrogen atmosphere.

It has now been discovered that alkylene glycol mono- Results of some yp expenments e ow 1n the thioethers (B-hydroxyalkyl thioethers) are produced in following table.

TABLE I Mole ratio Mercaptan consumed, Mole ratio, Example Mercaptan Alkylene oxide 1 Oxide to mer- Catalyst to Temp. C. Time, hr. percent mono/poly 2 eaptan mercaptan 2 0 06 100 21 100 32 4 0 06 100 21 100 52 8 0 06 100 21 100 55 4 0 06 100 23. 5 100 26 6 O 06 100 23. 5 100 46 6 do E0 6 0 06 100 23. 5 99.5 9 7 Phenyl. PO 4 04 100 19. i 100 88 E0 and P0 represent ethylene and 1, Z-propylene oxides respectively. 2 Thioether of monoand polyalkylene glycols, respectively.

high yield and conversion, and of high purity in that EXAMPLE 8 very little polyoxyalkylene thioether or unreacted mercaptan is present, by the reaction of a mercaptan with an alkylene oxide under carefully controlled conditions: 50 (1) The catalyst must be the sodium or lithium salt of the mercaptan to be etherified. Whereas the prior art NaOCH -4H O has considered these catalysts to be merely the equivalent of the potassium, cesium, calcium, barium or amine salts,

these latter catalysts are not equivalent to Na or Li salts EXAMPLE 9 in the present invention. If the catalyst is a Na salt a 2 When the experiment of Example 5 was repeated exsmall amount of water 1s usually essential for achieving cept that the catalyst was anhydrous NaOCHS the mole the desired selectivity of reaction. At least about 3 and ratio of products was only 0.09. When NaOCH -4H O preferably 4-8 moles of water per mole of catalyst 18 was used the product ratio was 195' When the experiment of Example 3 was repeated except that the catalyst was anhydrous NaOCH the mole ratio of products was only 0.06. In contrast, when was used, the product ratio was 25.

used In a series of experiments an alkylene oxide was re- The mole Yatlo of alkylene oxlde to mercaptan acted with n-butyl mercaptan under various conditions 511011161 be at fi 1111165, Preferably at least and with the results as shown in Table II. In every exfour mes, the Stolchlomemc ratloample the mercaptan was completely consumed. Here (3) The reaction temperature should not exceed about again it was found that the Li catalyst was most selec- 125 C. and is preferably not more than 100 C. tive (i.e. produced the highest ratio of monoglycol thio- Operation outside the above critical limits leads to ether to polyglycol thioether); that the presence of a the formation of increasing amounts of polyoxyalkylene small amount of water greatly improved the Na catalyst; thioethers. It is to be understood, of course, that the above and that the K catalyst was totally ineffective for making critical factors are interrelated and that good results can the monoglycol thioether.

TABLE II Mole ratio Example Alkylene Catalyst Temp., C. Time, hr. Mole ratio oxide 1 Oxide to Catalyst to mono/poly mercaptan mercaptan 6 0.06 so 2 co 6 0.06 so 2 10 6 0.06 80 2 ca 6 0.06 so 2 1 s .08 00 0.5 m s .08 90 6 m 8 .08 90 21.5 100 8 .08 00 1.0 .6 8 .08 90 .5 2.3 8 .08 90 .5 0

1 See footnotes to Table I.

Results similar to those shown above are obtained 5. The process of claim 4 wherein the alkylene oxide with other alkyl and aryl mercaptans, such as butyl, dois propylene oxide. decyl, octadecyl, allyl, Z-metylallyl, oleyl, propargyl ben- 6. The process of claim 5 wherein the mercaptan is zyl, cresyl, xylyl, napthyl, and the ar-halo and alkyl methyl mercaptan. analogs of the foregoing and, in general, with any mer- 7. The process of claim 1 wherein the mercaptan is captan susceptible of oxyalkylation by known methods. an allryl mercaptan of 1-18 carbon atoms. Similarly good results are obtained with other alkylene 8. The process of claim 7 wherein the alkylene oxide oxides, particularly butylene oxide. contains 24 carbon atoms.

I claim: 9. The process of claim 8 wherein the molar ratio of 1. In a process for making a fi-hydroxyalkyl thioether alkylene oxide to mercaptan is at least 4:.1. by the reaction of an alkylene oxide with a mercaptan, 10. The process of claim 9 wherein the reaction temthe improvement of effecting the reaction by contacting 25 perature is not more than 100 C. the oxide with the mercaptan in a molar ratio of at least 3:1, in the presence of a catalytic amount of the lithium References Cited or sodium salt of the mercaptan and at a temperature not UNITED STATES PATENTS exceeding 125 C.

2. The process of claim 1 wherein the catalyst is the 3,030,426 4/1962 Moseley et 260 6O9 XR t lSggllltgfSsaallttln combination with 3 8 moles of wa er per OTHER REFERENCES 3. The process of claim 1 wherein the alkylene oxide Reid! Chem- Bivalent 3111 1, PP- contains 2-4 carbon atoms.

CHARLES B. PARKER, Primary Examiner.

4. The process of claim 1 wherein the catalyst is the lithium salt.

D. R. PHILLIPS, Assistant Examiner. 

